I had a 6 year old golden retriever and a 2 year old chocolate lab,both were very healthy and up to date with shots. My wife let them out Friday morning to go to the bathroom and feed them. The chocolate was full of energy running around our yard as always, the golden seemed a little lethargic. She put them in our cellar for the day for fear of rain. My 12 year old daughter found them in our cellar at approx 5 PM. They were both laying at the bottom of our cellar stairs lifeless. I arrived home as fast as I could, (within an hour), the golden looked like he fought what had happened to him, he looked like he trashed about until he succummed to what took him. Our chocolate was lifeless laying right nest to him looking as though she just laid down and died next to him. There is nothing poisonious or toxic in our cellar, we had a fireman check our cellar for carbon monoxide and it turned up negative. We buried them in our flower garden that night, now all we want to know is what took our two beautiful dogs. Our family is devastated.